Information processing device, image transmission method and image transmission program

ABSTRACT

An information processing device includes a memory; and a processor coupled to the memory, wherein the processor executes a process comprising: drawing an image representing a processing result based on software into an image memory; identifying a high-frequency change area; animating an image of the high-frequency change area; adding time information to an image of a change area having a change or the image of the high-frequency change area animated, and transmits the image to a terminal device; receiving the time information from the terminal device; determining based on a difference between the received time information and a reception time of the time information whether image drawing delay occurs; and starting an animation of the change area when the image drawing delay occurs and the animation is not being executed or changes an image transmission interval when the image drawing delay occurs and the animation is being executed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2011-198799, filed on Sep. 12,2011, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to an informationprocessing device, an image transmission method and an imagetransmission program.

BACKGROUND

A system called as a thin client system is known. The thin client systemis configured so that a client is provided with only a minimum functionand resources such as applications and files are managed at a serverside.

According to the thin client system, a client acts as if the clientexecutes processing and holds data as a main body although a serveractually makes the client display results of processing executed by theserver and data held in the server.

As described above, when screen data which the client is made to displayare transmitted between the server and the client, congestion occurs ina network between the server and the client, so that transmission delaymay occur. This transmission delay of the network causes drawing of thescreen data transmitted from the server to be delayed at the clientside. Therefore, the response to operations executed at the client sidedeteriorates.

A dynamic encoding rate changing method for dynamically changing theencoding bit amount, sampling frequency, frame rate and the like ofmedia stream data in conformity with a network band has been disclosedas an example of a technology for suppressing transmission delay of anetwork. In this dynamic encoding rate changing method, encoding controldata are delivered between terminals every fixed period. For example, aterminal at the reception side receives encoding control data containinga header, a transmission time, a request sampling frequency, a requestframe rate, a request bit rate and the like from a terminal at thetransmission side. The terminal at the reception side generates encodingcontrol data containing optimum frame rate and bit rate based on ananalysis result of the network band analyzed by using the encodingcontrol data, and then transmits the optimum encoding control data tothe terminal at the transmission side. Thereafter, the terminal at thetransmission side encodes audio data and video data in accordance withthe encoding control data received from the terminal at the receptionside to generate media stream data, and transmits the generated mediastream data to the terminal at the reception side.

-   Patent Document 1: Japanese Laid-open Patent Publication No.    2004-214755

However, the thin client system has a problem that it is impossible tosuppress delay of drawing on a screen at a client side without damagingoperation response of the thin client as described below.

That is, it may be considered that the dynamic encoding rate changingmethod is applied to the thin client system to suppress the transmissiondelay of the network. When the network band between the server and theclient narrows under the application of the dynamic encoding ratechanging method, the frame rate of the screen data to be transmittedfrom the server to the client is uniformly reduced. This uniformreduction of the frame rate increases the update interval of the screenat the client side even when the drawing delay of the screen at theclient side can be suppressed by suppressing the transmission delay ofthe network, so that the operation response of the thin client isdeteriorated.

SUMMARY

According to an aspect of the embodiments, An information processingdevice includes a memory; and

a processor coupled to the memory, wherein the processor executes aprocess comprising: drawing an image representing a processing resultbased on software into an image memory that stores an image; identifyinga high-frequency change area in which a frequency of inter-frame changeof an image drawn in the image memory is not less than a predeterminedthreshold value; animating an image of the high-frequency change areaout of the image drawn in the image memory; adding time information toan image of a change area having a change or the image of thehigh-frequency change area animated out of the image drawn in the imagememory or any combination thereof, and transmits the image to a terminaldevice connected through a network; receiving the time information fromthe terminal device; determining based on a difference between thereceived time information and a reception time of the time informationwhether image drawing delay occurs in the terminal device; and startingan animation of the change area when the image drawing delay occurs andthe animation is not being executed or changes an image transmissioninterval to a transmission interval longer than a transmission intervalbefore the change when the image drawing delay occurs and the animationis being executed.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram depicting the functional construction of eachdevice contained in a thin client system according to a firstembodiment;

FIG. 2 is a diagram depicting the gist of division of a desktop screen;

FIG. 3A is a diagram depicting the gist of determination of a changefrequency of the desktop screen;

FIG. 3B is another diagram depicting the gist of the determination ofthe change frequency of the desktop screen;

FIG. 3C is another diagram depicting the gist of the determination ofthe change frequency of the desktop screen;

FIG. 4 is a diagram depicting the gist of correction of a mesh jointbody;

FIG. 5 is a diagram depicting the gist of combination of candidates of ahigh-frequency change area;

FIG. 6A is a diagram depicting the gist of notification of attributeinformation of the high-frequency change area;

FIG. 6B is another diagram depicting the gist of the notification of theattribute information of the high-frequency change area;

FIG. 6C is another diagram depicting the gist of the notification of theattribute information of the high-frequency change area;

FIG. 7 is a flowchart (1) depicting the procedure of image transmissionprocessing according to a first embodiment;

FIG. 8 is a flowchart (2) depicting the procedure of the imagetransmission processing according to the first embodiment;

FIG. 9 is a flowchart depicting the procedure of transmission intervalchange processing according to the first embodiment;

FIG. 10A is a diagram depicting the gist of extension of map clear;

FIG. 10B is another diagram depicting the gist of the extension of themap clear;

FIG. 11A is a diagram depicting the gist of suppression on contractionof a high-frequency change area;

FIG. 11B is another diagram depicting the gist of the suppression on thecontraction of the high-frequency change area; and

FIG. 12 is a diagram depicting an example of a computer for executing animage transmission program according to the first embodiment and asecond embodiment.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments will be explained with reference to accompanyingdrawings. These embodiments do not limit the disclosed technology. Therespective embodiments may be properly combined with one another to theextent that the processing contents thereof are not inconsistent withone another.

First Embodiment

System Construction

First, the construction of a thin client system according to the presentembodiment will be described. FIG. 1 is a block diagram depicting thefunctional construction of each device contained in the thin clientsystem according to the first embodiment.

In a thin client system 1 depicted in FIG. 1, the screen (display frame)displayed by a client terminal 20 is remotely controlled by a serverdevice 10. That is, according to the thin client system 1, the clientterminal 20 acts as if it executes processing and holds data as a mainbody although the server device 10 actually makes the client terminal 20display results of processing executed by the server device 10 and dataheld in the server device.

As depicted in FIG. 1, the thin client system 1 has the server device 10and the client terminal 20. In the example of FIG. 1, one clientterminal 20 is connected to one server device 10. However, any number ofclient terminals may be connected to one server device 10.

The server device 10 and the client terminal 20 are connected to eachother through a predetermined network so that they can mutuallycommunicate with each other. Any kinds of communication networks such asthe Internet, LAN (Local Area Network) and VPN (Virtual Private Network)may be adopted as the network irrespective of wired or wireless styles.It is assumed that an RFB (Remote Frame Buffer) protocol in VNC isadopted as a communication protocol between the server device 10 and theclient terminal 20, for example.

The server device 10 is a computer that supplies a service for remotelycontrolling a screen to be displayed on the client terminal 20. Anapplication for remote screen control for servers is installed orpre-installed in the server device 10. In the following description, theapplication for remote screen control for servers will be referred to as“the remote screen control application at the server side.”

The remote screen control application at the server side has a functionof supplying a remote screen control service as a basic function. As anexample, the remote screen control application at the server sideobtains operation information at the client terminal 20 and then makesan application operating in the device at the server side executeprocessing requested by the operation based on the operationinformation. Furthermore, the remote screen control application at theserver side generates a screen for displaying results of the processingexecuted by the application, and then transmits the generated screen tothe client terminal 20. At this time, the remote screen controlapplication at the server side transmits the area corresponding to anassembly of pixels at a portion at which a bit map image displayed onthe client terminal 20 before a present screen is generated is changed,that is, transmits an image of an update rectangle. In the followingdescription, a case where the image of the updated portion is formed ofa rectangular image will be described as an example. However, thedisclosed device is applicable to a case where the updated portion has ashape other than the rectangular shape.

In addition, the remote screen control application at the server sidealso has a function of compressing data of a portion having a largeinter-frame motion to compression type data suitable for moving picturesand then transmitting the compressed data to the client terminal 20. Asan example, the remote screen control application at the server sidedivides the screen generated from the result of the processing executedby the application into plural areas, and monitors the frequency ofchanges for each of the divided area. At this time, the remote screencontrol application at the server side transmits attribute informationof an area having a change frequency exceeding a threshold value, thatis, a high-frequency change area to the client terminal 20.

In addition to this processing, the remote screen control application atthe server side encodes the bit map image in the high-frequency changearea to MPEG type data such as MPEG-2 or MPEG-4, and then transmits theencoded data to the client terminal 20. In the foregoing description,the compression to the MPEG (Moving Picture Experts Group) type data isdescribed as an example. However, this embodiment is not limited to thisstyle, and for example, any compression encoding system such asMotion-JPEG (Joint Photographic Experts Group) may be adopted insofar asit is a compression type suitable for moving pictures.

The client terminal 20 is a computer at a reception side which receivesa remote screen control service from the server device 10. A fixedterminal such as a personal computer or a mobile terminal such as acellular phone, PHS (Personal Handyphone System) or PDA (PersonalDigital Assistant) may be adopted as an example of the client terminal20. A remote screen control application suitable for a client isinstalled or pre-installed in the client terminal 20. In the followingdescription, the application for remote screen control for a client willbe referred to as “remote screen control application at the clientside.”

The remote screen control application at the client side has a functionof notifying operation information received through various kinds ofinput devices such as a mouse and a keyboard to the server device 10. Asan example, the remote screen control application at the client sidenotifies, as the operation information, right or left click, doubleclick or drag of the mouse and the amount of movement of the mousecursor obtained through a moving operation of the mouse. As anotherexample, the amount of rotation of a mouse wheel, the type of a pushedkey of the keyboard and the like are also notified as the operationinformation.

Furthermore, the remote screen control application at the client sidehas a function of displaying images received from the server device 10on a predetermined display unit. As an example, when a bit map image ofan update rectangle is received from the server device 10, the remotescreen control application at the client side displays the image of theupdate rectangle while the image concerned is positioned to a changedportion of the previously displayed bit map image. As another example,when attribute information of a high-frequency change area is receivedfrom the server device 10, the remote screen control application at theclient side sets the area on the display screen corresponding to theposition contained in the attribute information as a blank area which isnot a display target of the bit map image (hereinafter referred to as an“out-of-display-target”). Under this condition, when receiving thecompression type data suitable for moving pictures, the remote screencontrol application at the client side decodes the data concerned andthen displays the decoded data on the blank area.

Construction of Server Device

Next, the functional construction of the server device according to thisembodiment will be described.

As depicted in FIG. 1, the server device 10 has an OS executioncontroller 11 a, an application execution controller 11 b, a graphicdriver 12, a frame buffer 13 and a remote screen controller 14. In theexample of FIG. 1, it is assumed that the thin client system containsvarious kinds of functional parts provided to an existing computer, forexample, functions such as various kinds of input devices and displaydevices in addition to the functional parts depicted in FIG. 1.

The OS execution controller 11 a is a processor for controllingexecution of OS (Operating System). As an example, the OS executioncontroller 11 a detects a start instruction of an application and acommand to the application from operation information obtained by anoperation information obtaining unit 14 a described later. For example,when detecting double click on an icon of an application, the OSexecution controller 11 a instructs the application execution controller11 b described later to start the application corresponding to the icon.Furthermore, when detecting an operation of requesting execution of acommand on an operation screen of an application being operated, thatis, on a so-called window, the OS execution controller 11 a instructsthe application execution controller 11 b to execute the command.

The application execution controller 11 b is a processor for controllingexecution of an application based on an instruction from the OSexecution controller 11 a. As an example, the application executioncontroller 11 b operates an application when the application isinstructed to start by the OS execution controller 11 a or execution ofa command is instructed to an application under operation. Theapplication execution controller 11 b requests the graphic driver 12described later to draw a display image of a processing result obtainedthrough execution of the application on the frame buffer 13. Whendrawing is requested to the graphic driver 12 as described above, theapplication execution controller 11 b notifies not only a display image,but also the drawing position of the display image to the graphic driver12.

The application executed by the application execution controller 11 bmay be pre-installed or installed after the server device 10 is shipped.Furthermore, the application may be an application operating under anetwork environment such as JAVA (registered trademark).

The graphic driver 12 is a processor for executing drawing processing onthe frame buffer 13. As an example, when accepting a drawing requestfrom the application execution controller 11 b, the graphic driver 12draws the display image as a processing result of the application in abit map format at a drawing position on the frame buffer 13 which isindicated by the application. In the foregoing description, the drawingrequest is accepted by the application. However, a drawing request fromthe OS execution controller 11 a may be accepted. For example, whenaccepting a drawing request based on the mouse cursor from the OSexecution controller 11 a, the graphic driver 12 draws the display imagebased on the mouse cursor in a bit map format at a drawing position onthe frame buffer 13 which is indicated by OS.

The frame buffer 13 is a memory device for storing a bit map image drawnby the graphic driver 12. A semiconductor memory element such as VRAM(Video Random Access Memory), RAM (Random Access Memory), ROM (Read OnlyMemory) or a flash memory is known as an example of the frame buffer 13.A memory device such as a hard disk or an optical disk may be adopted asthe frame buffer 13.

The remote screen controller 14 is a processor for supplying a remotescreen control service to the client terminal 20 through the remotescreen control application at the server side. As depicted in FIG. 1,the remote screen controller 14 has an operation information obtainingunit 14 a, a screen generator 14 b, a change frequency determining unit14 c and a high-frequency change area identifier 14 d. Furthermore, theremote screen controller 14 has a first encoder 14 e, a firsttransmitter 14 f, a second encoder 14 g, a second transmitter 14 h, aheader receiver 14 j, a drawing delay determining unit 14 k and atransmission controller 14 m.

The operation information obtaining unit 14 a is a processor forobtaining operation information from the client terminal 20. Right orleft click, double click or drag of the mouse and the amount of movementof the mouse cursor obtained through a moving operation of the mouse areprovided as an example of the operation information. Furthermore, theamount of rotation of a mouse wheel, the type of a pushed key of thekeyboard and the like are also notified as another example of theoperation information.

The screen generator 14 b is a processor for generating a screen imageto be displayed on a display unit 22 of the client terminal 20. As anexample, the screen generator 14 b starts the following processing everytime an update interval of the desktop screen, for example, 33 msecelapses. That is, the screen generator 14 b compares the desktop screendisplayed on the client terminal 20 at the previous frame generationtime with the desktop screen written on the frame buffer 13 at thepresent frame generation time. The screen generator 14 b joins andcombines pixels at a changed portion of the previous frame and shapesthe changed portion in a rectangular shape to generate an image of anupdate rectangle, and generates a packet for transmission of the updaterectangle.

The change frequency determining unit 14 c is a processor fordetermining the inter-frame change frequency every divided area withrespect to the image drawn on the frame buffer 13. As an example, thechange frequency determining unit 14 c accumulates an update rectanglegenerated by the screen generator 14 b into a working internal memory(not depicted) over a predetermined period. At this time, the changefrequency determining unit 14 c accumulates attribute informationcapable of specifying the position and size of the update rectangle, forexample, the coordinate of the apex at the upper left corner of theupdate rectangle and the width and height of the update rectangle. Theperiod for which the update rectangle is accumulated has correlationwith the identification precision of the high-frequency change area, anderroneous detection of the high-frequency change area is more greatlyreduced as the period is longer. In this embodiment, it is assumed thatthe image of the update rectangle is accumulated over 33 msec(milliseconds), for example.

At this time, when a predetermined period elapses from the accumulationof the image of the update rectangle, the change frequency determiningunit 14 c determines the change frequency of the desktop screen with amap obtained by dividing the desktop screen to be displayed on theclient terminal 20 in a mesh-like fashion.

FIG. 2 is a diagram depicting the gist of division of the desktopscreen. Reference numeral 30 in FIG. 2 represents a change frequencydetermining map. Reference numeral 31 in FIG. 2 represents a meshcontained in the map 30. Reference numeral 32 in FIG. 2 represents onepixel contained in a pixel block forming the mesh 31. In the exampledepicted in FIG. 2, it is assumed that the change frequency determiningunit 14 c divides the map 30 into blocks so that each block of 8pixels×8 pixels out of pixels occupying the map 30 is set as one mesh.In this case, 64 pixels contain one mesh.

Here, the change frequency determining unit 14 c successively developsthe image of the update rectangle onto the map for determining thechange frequency in accordance with the position and size of the updatedrectangle accumulated in the working internal memory. The changefrequency determining unit 14 c accumulates and adds the number of meshchanging times at a portion overlapped with the update rectangle on themap every time the update rectangle is developed onto the map. At thistime, when the update rectangle developed on the map is overlapped withthe pixels contained in the mesh over a predetermined number of times,the change frequency determining unit 14 c increments the number ofchange times of the mesh by 1. In this embodiment, it is assumed thatwhen the update rectangle is overlapped with at least one pixelcontained in the mesh, the number of change times of the mesh isincremented.

FIGS. 3A to 3C are diagrams depicting the gist of determination of thechange frequency of the desktop screen. Reference numerals 40A, 40B and40N in FIGS. 3A to 3C represent the change frequency determining maps.Reference numerals 41A and 41B in FIGS. 3A and 3B represent updaterectangles. In this embodiment, numerals depicted in meshes of the map40A represent the change frequencies of the meshes at the time point atwhich the update rectangle 41A is developed. Furthermore, numeralsdepicted in meshes of the map 40B represent the change frequencies ofthe meshes at the time point at which the update rectangle 41B isdeveloped. Furthermore, numerals depicted in meshes of the map 40Nrepresent the change frequencies of the meshes at the time point atwhich all update rectangles accumulated in the working internal memoryare developed. In FIGS. 3A to 3C, it is assumed that the number ofchange times of a mesh in which no numeral is depicted is zero.

As depicted in FIG. 3A, when the update rectangle 41A is developed onthe map 40A, the mesh of a hatched is overlapped with the updaterectangle 41A. Therefore, the change frequency determining unit 14 cincrements the update frequency of the mesh of the hatched portion oneby one. In this case, since the number of change times of each mesh isequal to zero, the number of change times of the hatched portion isincremented from 0 to 1. Furthermore, as depicted in FIG. 3B, when theupdate rectangle 41B is developed on the map 40B, the mesh of a hatchedportion is overlapped with the update rectangle 41B. Therefore, thechange frequency determining unit 14 c increments the number of changetimes of the mesh of the hatched portion one by one. In this case, thechange frequency of each mesh is equal to 1, and thus the number ofchange times of the hatched portion is incremented from 1 to 2. At thestage that all the update rectangles are developed on the map asdescribed above, the result of the map 40N depicted in FIG. 3C isobtained.

When the development of all the update rectangles accumulated in theworking internal memory on the map is finished, the change frequencydetermining unit 14 c obtains a mesh in which the number of changetimes, that is, the change frequency for the predetermined periodexceeds a threshold value. It means that the mesh of the hatched portionis obtained when the threshold value is set to “4” in the example ofFIG. 3C. As the threshold value is set to a higher value, a portion atwhich moving pictures are displayed on the desktop screen with highprobability can be encoded by a second encoder 14 g described later.With respect to the threshold value, an end user may select a valuewhich is stepwise set by a developer of the remote screen controlapplication, or an end user may directly set a value.

The high-frequency change area identifier 14 d is a processor foridentifying, as a high-frequency change area, an area which is changedwith high frequency on the desktop screen displayed on the clientterminal 20.

Specifically, when meshes whose number of change times exceed thethreshold value are obtained by the change frequency determining unit 14c, the high-frequency change area identifier 14 d corrects a mesh jointbody obtained by joining adjacent meshes to a rectangle. As an example,the high-frequency change area identifier 14 d derives an interpolationarea to be interpolated to the mesh joint body, and then added theinterpolation area to the joint body, whereby the mesh joint body iscorrected to a rectangle. An algorithm for deriving an area with whichthe joint body of meshes can be shaped to a rectangle by the minimuminterpolation is applied to derive the interpolation area.

FIG. 4 is a diagram depicting the gist of correction of the mesh jointbody. Reference numeral 51 in FIG. 4 represents a mesh joint body beforecorrection, reference numeral 52 in FIG. 4 represents an interpolationarea, and reference numeral 53 in FIG. 4 represents a rectangle afterthe correction. As depicted in FIG. 4, the high-frequency change areaidentifier 14 d adds the mesh joint body 51 with the interpolation area52 to correct the mesh joint body 51 to the rectangle 53. At this stage,the synthesis of a rectangle described later has not been completed, andthe rectangle 53 has not yet been settled as the high-frequency changearea. Therefore, the rectangle after the correction is called as acandidate of the high-frequency change area.

When plural candidates of the high-frequency change area exist, thehigh-frequency change area identifier 14 d synthesizes a rectanglecontaining plural candidates of the high-frequency change area which areselected so that the distance between the candidates is equal to apredetermined value or less. Here, the distance between the candidatesrepresents the shortest distance of the rectangles after correction. Asan example, the high-frequency change area identifier 14 d derives aninterpolation area to be filled among the respective candidates when thecandidates of the high-frequency change area are combined with oneanother, and then adds the candidates of the high-frequency change areawith the interpolation area, thereby synthesizing the rectanglecontaining the candidates of the high-frequency change area. Analgorithm for deriving an area with which the candidates of thehigh-frequency change area are shaped to a combination body by theminimum interpolation is applied to derive the interpolation area.

FIG. 5 is a diagram depicting the gist of combination of candidates of ahigh-frequency change area. Reference numerals 61A and 61B in FIG. 5represent candidates of the high-frequency change area, referencenumeral 62 in FIG. 5 represents an interpolation area, and referencenumeral 63 in FIG. 5 represents a combination body of the candidate 61Aof the high-frequency change area and the candidate 61B of thehigh-frequency change area. As depicted in FIG. 5, the high-frequencychange area identifier 14 d adds the interpolation area 62 to thecandidate 61A of the high-frequency change area and the candidate 61B ofthe high-frequency change area the distance between which is equal to adistance d or less, thereby synthesizing the combination body 63containing the candidate 61A of the high-frequency change area and thecandidate 61B of the high-frequency change area. The high-frequencychange area identifier 14 d identifies the thus-obtained combinationbody as the high-frequency change area.

When identifying the high-frequency change area as described above, thehigh-frequency change area identifier 14 d transmits to the clientterminal 20 attribute information with which the position and size ofthe high-frequency change area can be specified, whereby the portioncorresponding to the high-frequency change area out of the bit map imageof the desktop screen displayed on the client terminal 20 is displayedas a blank. Thereafter, the high-frequency change area identifier 14 dclears the number of change times of meshes mapped in the workinginternal memory. The high-frequency change area identifier 14 dregisters the attribute information of the high-frequency change area inthe working internal memory.

FIGS. 6A to 6C are diagrams depicting the gist of notification of theattribute information of the high-frequency change area. Referencenumeral 70A in FIG. 6A represents an example of the desktop screen drawnon the frame buffer 13, and reference numerals 70B and 70C in FIGS. 6Bto 6C represent change frequency determining maps. Reference numeral 71in FIG. 6A represents a browser screen (window), reference numeral 72 inFIG. 6A represents a moving picture reproducing screen (window),reference numeral 73 in FIG. 6B represents a movement locus of themouse, and reference numeral 74 in FIG. 6B represents a moving picturereproducing area based on an application.

As depicted in FIG. 6A, the desktop screen 70A contains the browserscreen 71 and the moving picture reproducing screen 72. When atime-dependent variation is pursued from the desktop screen 70A, noupdate rectangle is detected on the browser screen 71 as a still pictureand update rectangles associated with the movement locus 73 of the mouseand the moving picture reproducing area 74 are detected as depicted inFIG. 6B. In this case, it is assumed that a mesh in which the number ofchange times exceed the threshold value in the moving picturereproducing area 74, that is, a hatched portion in FIG. 6B is identifiedby the high-frequency change area identifier 14 d. In this case, thehigh-frequency change area identifier 14 d transmits the coordinate(x,y) of the apex at the upper left corner of the high-frequency changearea of the hatched portion in FIG. 6C and the width w and height h ofthe high-frequency change area as the attribute information of thehigh-frequency change area to the client terminal 20.

In this embodiment, the coordinate of the apex at the upper left corneris adopted as a point for specifying the position of the high-frequencychange area, but another apex may be adopted. Any point other than theapex, for example, the center of gravity may be adopted insofar as itcan specify the position of the high-frequency change area. Furthermore,the upper left corner on the screen is set as the origin of thecoordinate axis XY, but any point within the screen or out of the screenmay be adopted as the origin.

When the high-frequency change area is detected at a part of the desktopscreen as described above, animation for moving pictures of thehigh-frequency change area on the desktop screen is started. In thiscase, the bit map image of the portion corresponding to thehigh-frequency change area out of the bit map image drawn on the framebuffer 13 is input to the first encoder 14 e described later by thetransmission controller 14 m. On the other hand, with respect to anupdate rectangle which is not contained in the high-frequency changearea, it may be compressed in a still picture compression format as inthe case of the stage before the animation for moving pictures isstarted. That is, the image of the update rectangle which is notcontained in the high-frequency change area out of the bit map imagedrawn on the frame buffer 13 is input to the second encoder 14 gdescribed later by the transmission controller 14 m described later.

The first encoder 14 e is a processor for encoding the image of theupdate rectangle input from the transmission controller 14 m describedlater in the still picture compression format. As an example, the firstencoder 14 e compresses the image of each update rectangle in JPEG toencode the image to encoded data of the still picture. In thisembodiment, JPEG is exemplified as the still picture compression format,but another format such as GIF (Graphic Interchange Format) or PNG(Portable Network Graphics) may be applied.

The first transmitter 14 f is a processor for transmitting the encodeddata of the update rectangle encoded by the first encoder 14 e to theclient terminal 20. As an example, upon instruction of addition ofheader information by the transmission controller 14 m described later,the first transmitter 14 f adds the encoded data with header informationon frame ID, a timestamp of a transmission time and the like and thentransmits them to the client terminal 20 when the encoded data of theupdate rectangle is transmitted to the client terminal 20. At this time,the first transmitter 14 f can add the header information to the encodeddata of all the update rectangles encoded by the first encoder 14 e, butit may add the header information to the encoded data of at least oneupdate rectangle out of the encoded data of the update rectangles. Inthe following description, it is assumed as an example that the firsttransmitter 14 f adds the header information to only the encoded data ofthe finally transmitted update rectangle out of the update rectanglesgenerated from the same bit map image. The “frame ID” represents theframe number of the bit map image drawn on the frame buffer 13. The“transmission time” represents the time at which the encoded data of theupdate rectangle is transmitted by the first transmitter 14 f.

When the header information is added to the encoded data of one updaterectangle out of the encoded data of all the update rectangles, thefollowing effect can be implemented. That is, only the headerinformation is returned after the encoded data of moving pictures aredecoded and a screen is drawn at the client terminal 20, whereby thedrawing delay at the client side can be monitored on a frame basis bythe drawing delay determining unit 14 k described later. Therefore, thedrawing delay can be monitored with harmonizing the tradeoff between themonitoring precision of the drawing delay and each of the traffic of thenetwork and the load of the client terminal 20.

The second encoder 14 g is a processor for encoding an image input fromthe transmission controller 14 m described later in a moving picturecompression format. As an example, the second encoder 14 g compresses animage of a high-frequency change area or change area in MPEG to encodethe image to encoded data of a moving picture. In this embodiment, MPEGis exemplified as the moving picture compression format, but anotherformat such as Motion-JPEG may be applied.

When the high-frequency change area is identified by the high-frequencychange area identifier 14 d, the image of the high-frequency change areais input from the transmission controller 14 m described later to thesecond encoder 14 g. When the animation for moving pictures is forcedlystarted as described above although the high-frequency change area isnot identified, the change area determining processing is brought to anend at this stage, and the image of a change area changed within thechange frequency determining map is input by the transmission controller14 m described later. That is, at the stage that the animation formoving pictures is forcedly started, the generation of a mesh joint bodydescribed above, the correction of the mesh joint body to a rectangle,the synthesis of a rectangle and the like are performed on meshes inwhich changes occur without performing the threshold value determinationbased on the number of change times from the change frequencydetermining map. The thus-obtained image of the change area is input bythe transmission controller 14 m described later.

The second transmitter 14 h is a processor for transmitting the encodeddata of the moving picture encoded by the second encoder 14 g to theclient terminal 20. As an example, when addition of header informationis instructed by the transmission controller 14 m, the secondtransmitter 14 h adds the header information to at least one encodeddata out of the encoded data of moving pictures. When the headerinformation is added to the encoded data of the moving pictures asdescribed above, only the header information is returned after theencoded data of the moving pictures are decoded and the screen is drawnat the client terminal 20, whereby the following effect can beimplemented. That is, when the encoded data of the moving pictures aretransmitted, the amount of drawing processing executed for the update ofthe screen increases at the client terminal 20. As described above, thedrawing delay at the client terminal 20 can be monitored based on theprocessing load for the drawing of the encoded data of the movingpictures which is liable to become a bottleneck with respect to thedrawing delay in a situation that the drawing delay occurs at the clientterminal 20 with high probability.

The header receiver 14 j is a processor for receiving the headerinformation returned from the client terminal 20. The header receiver 14j outputs the header information received from the client terminal 20 tothe drawing delay determining unit 14 k described later.

The drawing delay determining unit 14 k is a processor for determiningbased on the difference between the transmission time contained in theheader information received by the header receiver 14 j and thereception time of the returned header information whether screen drawingdelay occurs at the client terminal 20.

As an example, the drawing delay determining unit 14 k calculates thetime difference between the transmission time and the reception time bysubtracting the transmission time contained in the header informationfrom the reception time at which the returned header information isreceived. Furthermore, the drawing delay determining unit 14 kdetermines whether the thus-calculated time difference between thetransmission time and the reception time is not less than apredetermined threshold value Th1, for example, 100 msec. As describedabove, based on whether the time difference is not less than thethreshold value Th1, it can be determined whether transmission delay ofthe network and eventually drawing delay caused by the transmissiondelay occurs. At this time, when the time difference between thetransmission time and the reception time is less than the thresholdvalue Th1, the drawing delay determining unit 14 k determines whetherthe time difference between the transmission time and the reception timeis not more than a predetermined threshold value Th2, for example, 50msec over a predetermined number of frames, for example, five frames. Asdescribed above, based on whether the time difference is continuouslynot more than the threshold value Th2 among frames, it can be determinedwhether the transmission interval can be restored to an originaltransmission interval when the transmission controller 14 m describedlater drops the transmission interval of the encoded data of movingpictures.

The transmission controller 14 m is a processor for controllingtransmission of the desktop screen. The transmission controller 14 mexecutes transmission control of the update rectangle and the encodeddata of the moving picture by using a transmission interval register(not depicted) in which a still picture transmission interval F1 and amoving picture transmission interval F2 are set. Here, the “transmissioninterval F1” represents an interval at which the encoded data of stillpictures are transmitted from the server device 10 to the clientterminal 20. The “transmission interval F2” represents an interval atwhich the encoded data of moving pictures are transmitted from theserver device 10 to the client terminal 20. For example, 33 msec is setas initial values for the still picture transmission interval F1 and themoving picture transmission interval F2 in the transmission intervalregister.

As an example, the transmission controller 14 m controls the change ofthe moving picture transmission interval F2 in accordance with thedetermination result of the drawing delay by the drawing delaydetermining unit 14 k. Specifically, when the drawing delay determiningunit 14 k determines that the time difference is not less than thethreshold value Th1, the transmission controller 14 m determines whetherthe animation for moving pictures is being executed. At this time, whenthe animation has not yet been executed, it can be estimated that theencoded data of the still picture of an update rectangle having a largedata amount increases the traffic of the network with high probability.In this case, the transmission controller 14 m brings the processing ofdetermining the change frequency to an end at the stage that thedetermination concerned is executed, and inputs to the second encoder 14g the image of a change area which is changed in the change frequencydetermining map, thereby forcedly starting the animation. As describedabove, the control for reducing the traffic of the network is executedby executing the encoding based on the moving picture having a highercompression rate than the encoding based on the still picture. On theother hand, when the animation is executed, it can be estimated that theperformance of the client terminal 20 is too deficient to decode theencoded data of the moving picture at the present frame rate. In thiscase, the transmission controller 14 m changes the moving picturetransmission interval F2 to a longer transmission interval than thatbefore the change. For example, the transmission controller 14 m changesthe transmission interval F2 from 33 msec as the initial value to 100msec. Accordingly, the amount of decoding processing executed by theclient terminal 20 is matched with the performance of the clientterminal 20, whereby the drawing delay of the screen at the clientterminal 20 is suppressed. When the transmission interval F2 has beenalready lowered from 33 msec as the initial value to 100 msec, 100 msecis maintained.

As described above, when the still picture of the update rectanglecompresses the band of the network with high probability, the animationis forcedly started, and when the performance of the client terminal 20does not follow the decode of moving pictures, the transmission intervalof the encoded data of the moving pictures is lengthened. Therefore, thedrawing delay of the screen at the client side can be suppressed whilereduction of the operation response of the thin client is suppressed.

Furthermore, when it is determined by the drawing delay determining unit14 k that the time difference is not more than the threshold value Th2over a predetermined number of frames, the transmission controller 14 mreturns the moving picture transmission interval F2 to the transmissioninterval before the change. For example, the transmission interval F2which has been reduced to 100 msec is returned to 33 msec as the initialvalue by the transmission controller 14 m. This is because when the timedifference is not more than the threshold value Th2 over a predeterminednumber of frames, the transmission of the encoded data of still picturesand moving pictures and the decoding of the encoded data of the stillpictures and the moving pictures can be estimated to be stable.

As another example, the transmission controller 14 m inputs an image tothe first encoder 14 e or the second encoder 14 g. This will bespecifically described below. First, the transmission controller 14 mreads out the transmission interval F1 and the transmission interval F2from the transmission interval register. In this case, when theanimation is being executed, the transmission controller 14 m determineswhether a transmission lapse time t2 elapsing from previous transmissionof encoded data of moving pictures reaches the transmission interval F2,that is, whether the transmission lapse time t2≧the transmissioninterval F2 is satisfied or not. At this time, when the transmissionlapse time t2≧the transmission interval F2 is satisfied, thetransmission controller 14 m inputs the image of a high-frequency changearea or change area to the second encoder 14 g. On the other hand, whenthe transmission lapse time t2<the transmission interval F2 issatisfied, the transmission controller 14 m does not input the image ofthe high-frequency change area or change area to the second encoder 14g, and waits until the transmission interval F2 lapses.

The transmission controller 14 m determines whether the transmissionlapse time t1 elapsing from the previous transmission of the encodeddata of the image of an upgrade rectangle reaches the transmissioninterval F1, that is, whether the transmission lapse time t1≧thetransmission interval F1 is satisfied. At this time, when thetransmission lapse time t1≧the transmission interval F1, thetransmission controller 14 m inputs to the first encoder 14 e the imagesof update rectangles which are not contained in the high-frequencychange area. On the other hand, when the transmission lapse time t1<thetransmission interval F1, the transmission controller 14 m does notinput the images of update rectangles to the first encoder 14 e, andwaits until the transmission interval F1 elapses.

Thereafter, the transmission controller 14 m determines whether any oneof the image of the update rectangle and the image of the high-frequencychange area or change area is input to the first encoder 14 e or thesecond encoder 14 g, that is, whether there is any transmission data. Atthis time, when some transmission data exists, the transmissioncontroller 14 m makes either the first transmitter 14 f or the secondtransmitter 14 h add header information. For example, when an image isinput to only the first encoder 14 e, or when an image is input both thefirst encoder 14 e and the second encoder 14 g, the transmissioncontroller 14 m instructs the first transmitter 14 f to add the headerinformation. On the other hand, when an image is input to only thesecond encoder 14 g, the transmission controller 14 m instructs thesecond transmitter 14 h to add header information. Furthermore, when noimage is input to each of the first encoder 14 e and the second encoder14 g, the transmission controller 14 m gives no instruction of addingheader information because there is no transmission data.

Various kinds of integrated circuits and electronic circuits may beadopted for the OS execution controller 11 a, the application executioncontroller 11 b, the graphic driver 12 and the remote screen controller14. Some parts of the functional parts contained in the remote screencontroller 14 may be implemented by other integrated circuits orelectronic circuits. For example, ASIC (Application Specific IntegratedCircuit) or FPGA (Field Programmable Gate Array) may be adopted as theintegrated circuits. Furthermore, CPU (Central Processing Unit), MPU(Micro Processing Unit) or the like may be adopted as the electroniccircuit.

Construction of Client Terminal

Next, the functional construction of the client terminal according tothis embodiment will be described. As depicted in FIG. 1, the clientterminal 20 has an input unit 21, a display unit 22, a remote screencontroller 23 at the client side. In the example of FIG. 1, it isassumed that the various kinds of functional parts provided to anexisting computer, for example, functions such as an audio output unitand the like are provided in addition to the functional parts depictedin FIG. 1.

The input unit 21 is an input device for accepting various kinds ofinformation, for example, an instruction input to the remote screencontroller 23 at the client side described later. As an example, akeyboard or a mouse may be applied. The display unit 22 described laterimplements a pointing device function in cooperation with the mouse.

The display unit 22 is a display device for displaying a desktop screenand the like transmitted from the server device 10, for example, and amonitor, a display or a touch panel may be applied.

The remote screen controller 23 is a processor for receiving a remotescreen control service supplied form the server device 10 through theremote screen control application at the client side. As depicted inFIG. 1, the remote screen controller 23 has an operation informationnotifying unit 23 a, a first receiver 23 b, a first decoder 23 c and afirst display controller 23 d. Furthermore, the remote screen controller23 has a second receiver 23 e, a second decoder 23 f, a second displaycontroller 23 g and a header return unit 23 h.

The operation information notifying unit 23 a is a processor fornotifying the operation information based on the input unit 21 to theserver device 10. As an example, the operation information notifyingunit 23 a notifies right or left click, double click and drag of themouse, the movement amount of the mouse cursor obtained through themoving operation of the mouse and the like as operation information. Asanother example, the operation information notifying unit 23 a notifiesthe rotational amount of the mouse wheel, the type of a pushed key ofthe keyboard and the like as the operation information.

The first receiver 23 b is a processor for receiving the encoded data ofthe update rectangle transmitted by the first transmitter 14 f of theserver device 10. As an example, the first receiver 23 b takes out theheader information from the encoded data of the update rectanglereceived from the server device 10, and outputs the header informationto the first display controller 23 d while the first receiver 23 boutputs the encoded data of the update rectangle to the first decoder 23c. Accordingly, decoding is skipped for only the header information. Thefirst receiver 23 b receives the attribute information of thehigh-frequency change area transmitted by the high-frequency change areaidentifier 14 d of the server device 10.

The first decoder 23 c is a processor for decoding the encoded data ofthe update rectangle received by the first receiver 23 b. A decoderhaving a decoding system which is matched with the encoding system setup in the server device 10 is mounted in the first decoder 23 c.

The first display controller 23 d is a processor for making the displayunit 22 display the image of the update rectangle decoded by the firstdecoder 23 c. As an example, the first display controller 23 d makes thedisplay unit 22 display the bit map image of the update rectangle on ascreen area of the display unit 22 which corresponds to the position andthe size contained in the attribute information of the update rectanglereceived by the first receiver 23 b. Furthermore, when the attributeinformation of the high-frequency change area is received by the firstreceiver 23 b, the first display controller 23 d executes the followingprocessing. That is, the first display controller 23 d sets the screenarea of the display unit 22 corresponding to the position and size ofthe high-frequency change area contained in the attribute information ofthe high-frequency change area as a blank area which is an out-of-targetwith respect to display of the bit map image. When the drawing of thescreen is finished as described above, the first display controller 23 doutputs the header information input from the first receiver 23 b to theheader return unit 23 h described later.

The second receiver 23 e is a processor for receiving the encoded dataof the moving pictures transmitted by the second transmitter 14 h of theserver device 10. The second receiver 23 e receives the attributeinformation of the high-frequency change area transmitted by thehigh-frequency change area identifier 14 d of the server device 10.

The second decoder 23 f is a processor for decoding the encoded data ofthe moving pictures received by the second receiver 23 e. A decoderhaving a decoding system matched with the encoding format installed inthe server device 10 is mounted in the second decoder 23 f.

The second display controller 23 g is a processor for making the displayunit 22 display the image of the high-frequency change area or changearea decoded by the second decoder 23 f based on the attributeinformation of the high-frequency change area which is received by thesecond receiver 23 e. As an example, the second display controller 23 gmakes the display unit 22 display the image of the moving pictures ofthe high-frequency change area on the screen area of the display unit 22corresponding to the position and size of the high-frequency change areacontained in the attribute information of the high-frequency changearea. When header information is added to the encoded data of the movingpictures, the header information is output to the header return unit 23h described later at the stage that the decoding and the drawing of thescreen are finished as in the case of the still pictures.

The header return unit 23 h is a processor for returning the headerinformation to the server device 10. As an example, the header returnunit 23 h transmits the header information input from the server device10 through the first receiver 23 b and the first display controller 23 dto the server device 10. As described above, by returning the headerinformation, the transmission delay of the network and eventually thedrawing delay of the screen can be estimated from the time differencebetween the transmission time and the return time at the server device10 side.

Various kinds of integrated circuits and electronic circuits may beadopted for the remote screen controller 23 at the client side.Furthermore, some parts of functional parts contained in the remotescreen controller 23 may be implemented by other integrated circuits orelectronic circuits. For example, ASIC or FPGA may be adopted as theintegrated circuits, and CPU, MPU or the like may be adopted as theelectronic circuits.

Flow of Processing

Next, the procedure of the processing of the thin client systemaccording to this embodiment will be described. In the followingdescription, (1) image transmission processing executed in the serverdevice 10 is described, and then (2) transmission interval changingprocessing will be described.

(1) Image Transmission Processing

FIGS. 7 and 8 are flowcharts depicting the procedure of the imagetransmission processing according to the first embodiment. The imagetransmission processing is executed by the server device 10, and it isrepetitively executed insofar as the client terminal 20 is beingoperated.

As depicted in FIG. 7, the server device 10 executes initialization ofwriting the initial value “33 msec” into the still picture transmissioninterval F1 and the moving picture transmission interval F2 stored inthe transmission interval register (step S101).

Thereafter, the server device 10 executes the following processing whena bit map image is drawn on the frame buffer 13 and an image of anupdate rectangle which is obtained by joining pixels at a portionchanged from a previous frame and then shaped to a rectangle isgenerated (Yes in step S102). That is, the server device 10 reads outthe still picture transmission interval F1 and the moving picturetransmission interval F2 from the transmission interval register (stepS103).

The server device 10 generates a packet for update rectangletransmission from a previously generated update rectangle image (stepS104), and accumulates the generated update rectangle into a workinginternal memory (not depicted) (step S105).

At this time, when a predetermined period does not elapse from the startof the accumulation of update rectangle (No in step S106), subsequentprocessing concerning identification of the high-frequency change areais skipped, and the processing goes to step S115 depicted in FIG. 8.

On the other hand, when the predetermined period elapses from the startof the accumulation of the update rectangle (Yes in step S106), theserver device 10 executes the following processing. That is, the serverdevice 10 successively develops the images of the update rectangles onthe change frequency determining map according to the positions andsizes of the update rectangles accumulated in the working internalmemory (step S107). The server device 10 obtains meshes having changefrequencies exceeding the threshold value out of the meshes contained inthe change frequency determining map (step S108).

Thereafter, the server device 10 determines whether any mesh whosechange frequency exceeds the threshold value is obtained (step S109). Atthis time, when there does not exist any mesh whose change frequencyexceeds the threshold value (No in step S109), no high-frequency changearea exists on the desktop screen. Therefore, the subsequent processingconcerning the identification of the high-frequency change area isskipped, and the processing goes to step S114.

On the other hand, when a mesh whose change area exceeds the thresholdvalue exists (Yes in step S109), the server device 10 corrects a meshjoint body obtained by joining adjacent meshes to a rectangle (stepS110).

When plural corrected rectangles, that is, plural high-frequency changearea candidates exist (Yes in step S111), the server device 10 combinescorrected rectangles so as to synthesize a rectangle containing pluralhigh-frequency change area candidates which are spaced from one anotherat a predetermined distance value or less (step S112). When pluralhigh-frequency change areas do not exist (No in step S111), thesynthesis of the rectangle is not performed, and the processing goes tostep S113.

Subsequently, the server device 10 transmits to the client terminal 20the attribute information from which the position and size of thehigh-frequency change area can be specified (step S113). Then, theserver device 10 clears the number of change times of the meshes mappedin the working internal memory (step S114).

Thereafter, as depicted in FIG. 8, when the animation is being executed(Yes in step S115), the server device 10 determines whether the movingpicture transmission lapse time t2 reaches the transmission interval F2,that is, whether the transmission lapse time t2≧the transmissioninterval F2 is satisfied (step S116).

At this time, when the transmission lapse time t2≧the transmissioninterval F2 is satisfied (Yes in step S116), the server device 10encodes the image of the high-frequency change area or change area tothe moving picture encoded data (step S117).

On the other hand, when the transmission lapse time t2<the transmissioninterval F2 (No in step S116), the server device 10 skips the step S117and shifts the processing to step S118 for broadening the transmissioninterval of the encoded data of the moving pictures.

Subsequently, the server device 10 determines whether the still picturetransmission lapse time t1 reaches the transmission interval F1, thatis, whether the transmission lapse time t1≧the transmission interval F1(step S118).

At this time, when the transmission lapse time t1≧the transmissioninterval F1 is satisfied (Yes in step S118), the server device 10encodes the update rectangle image to the still image encoded data (stepS119).

On the other hand, when the transmission lapse time t1<the transmissioninterval F1 (No in step S118), the server device 10 skips the step S119and shifts the processing to step S120 for broadening the transmissioninterval of the encoded data of the still pictures.

When the encoded data of the still images or moving pictures encodedthrough the processing of the step S117 or S119, that is, transmissiondata exist (Yes in step S120), the server device 10 executes thefollowing processing. That is, after the server device 10 adds theheader information containing the frame ID and the transmission time tothe encoded data of either a still image or a moving picture (stepS121), the server device 10 transmits the transmission data of the stillpicture encoded data and/or the moving picture encoded data to theclient terminal 20 (step S122).

Thereafter, the server device 10 returns to the processing of the stepS102, and repetitively executes the processing from the step S102 to thestep S122 insofar as the client terminal 20 is being operated. When thepower of the client terminal 20 is shut down, the server device 10finishes the processing.

(2) Transmission Interval Changing Processing

Next, transmission interval changing processing according to theembodiment will be described. FIG. 9 is a flowchart depicting theprocedure of the transmission interval changing processing according tothe first embodiment. The transmission interval changing processing isexecuted by the server device 10, and it is repetitively executedinsofar as the client terminal 20 is being operated.

As depicted in FIG. 9, when the return of the header information isreceived (Yes in step S201), the server device 10 subtracts thetransmission time contained in the header information from the receptiontime at which the return of the header information is received, therebycalculating the time difference between the transmission time and thereception time (step S202).

The server device 10 determines whether the time difference between thetransmission time and the reception time calculated as in the case ofthe step S201 is equal to the threshold value Th1 or more (step S203).At this time, when the time difference is not less than the Th1 (Yes instep S203), the server device 10 further determines whether theanimation is being executed (step S204).

Here, when the animation has not yet been executed (No in step S204), itcan be estimated that the encoded data of the still image of the updaterectangle having a large data amount increases the traffic of thenetwork with high probability. In this case, at the stage that the abovedetermination is executed, the server device 10 brings the processing ofdetermining the change frequency to an end, and inputs the image of thechange area changed within the change frequency determining map to thesecond encoder 14 g, thereby forcedly starting the animation (stepS205).

On the other hand, when the animation is being executed (Yes in stepS204), it can be estimated that the performance of the client terminal20 is too deficient to decode the encoded data of the moving picture atthe present frame rate. In this case, the server device 10 changes themoving picture transmission interval F2 to a longer transmissioninterval than that before the change (step S206).

Furthermore, when the time difference between the transmission time andthe reception time is less than the threshold value Th1 (No in stepS203), the server device 10 further determines whether the timedifference between the transmission time and the reception time is equalor less than the threshold value Th2 over a predetermined number offrames (step S207).

At this time, when the time difference is not more than the thresholdvalue Th2 over the predetermined number of frames (Yes in step S207),the server device 10 returns the moving picture transmission interval F2to the transmission interval before the change (step S208). When thetime difference is more than the threshold value Th2 over thepredetermined number of frames (No in step S207), the server device 10does not return the transmission interval, and shifts the processing tothe step S201.

When the processing of the step S205, the step S206 or the step S208 isfinished, the server device 10 returns the processing to the step S201,and repetitively executes the processing from the step S201 to the stepS208 insofar as the client terminal 20 is being operated. When the powerof the client terminal 20 is shut down, the server device 10 finishesthe processing.

Effect of First Embodiment

As described above, in the server device 10 according to thisembodiment, when the still picture of the update rectangle compressesthe band of the network with high probability, the animation is forcedlystarted. Furthermore, in the server device 10 according to thisembodiment, when the performance of the client terminal 20 does notfollow the decoding of moving pictures, the transmission interval of theencoded data of the moving pictures is lengthened. Accordingly,according to the server device 10 of this embodiment, the drawing delayof the screen at the client side can be suppressed with suppressing thereduction of the operation response of the thin client.

Furthermore, when plural update area images exist, the server device 10according to this embodiment adds the header information to the image ofat least one update area. Therefore, in the server device 10 accordingto this embodiment, the drawing delay at the client side can bemonitored on a frame basis by returning only the header informationafter the decoding of the moving picture encoded data and the drawing ofthe screen are performed at the client terminal 20. Accordingly,according to the server device 10 of this embodiment, the drawing delaycan be monitored with harmonizing the tradeoff between the traffic ofthe network and each of the load of the client terminal 20 and themonitoring precision of the drawing delay.

Still furthermore, when no drawing delay occurs in the client terminal20, the server device 10 according to this embodiment returns thetransmission interval F2 for transmitting the moving picture encodeddata to the transmission interval before the change. Accordingly,according to the server device 10 of this embodiment, when the clientterminal 20 is restored from the transmission delay of the network orthe drawing delay, the original operation response can be suppliedwithout saving the transmission of the moving picture encoded data.

Second Embodiment

The embodiment relating to the disclosed device has been describedabove. However, the present invention may be implemented according tovarious different modes in addition to the foregoing embodiment.Therefore, another embodiment contained in the present invention will bedescribed hereunder.

Extension of Map Clear

For example, in the first embodiment described above, the high-frequencychange area identifier 14 d clears the change frequency determining mapin conformity with (in synchronization with) the update rectangleaccumulating period. However, the timing at which the change frequencydetermining map is cleared is not limited to the above style.

As an example, even after the change frequency drops and does not exceedthe threshold value in an area identified as a high-frequency changearea, the high-frequency change area identifier 14 d may continuouslyidentify the area as the high-frequency change area over a predeterminedperiod.

FIGS. 10A and 10B are diagrams depicting the gist of extension of mapclear. FIG. 10A depicts a change frequency determining map 80A at thetime point when a high-frequency change area is first identified, and anidentification result 81A of the high-frequency change area at that timepoint. Furthermore, FIG. 10B depicts a change frequency determining map80B at a specific time point within a predetermined period from the timewhen the high-frequency change area is first identified, and anidentification result 81A of the high-frequency change area at that timepoint.

As depicted in FIG. 10A, when a mesh joint body having the number ofchange times exceeding a threshold value is obtained on the map 80A andan identification result 81A of a high-frequency change area isobtained, the identification result 81A is taken over for apredetermined period even when there is not subsequently obtained anymesh joint body having the number of change times exceeding thethreshold value. That is, as depicted in FIG. 10B, the identificationresult 81A of the high-frequency change area is taken over within thepredetermined period after the identification result 81A of thehigh-frequency change area is first identified even when there is notobtained any mesh joint body having the number of change times exceedingthe threshold value on the map 80A. An end user may select as the“threshold value” a value which is stepwise set by the developer of theremote screen control application at the server side, or the end usermay directly set the “threshold value.”

Accordingly, even when motion is intermittently stopped in an area wheremoving pictures are actually reproduced, the high-frequency change areais not intermittently identified, so that frame drop of images can beprevented from intermittently occurring in the high-frequency changearea. Furthermore, the identification result of the high-frequencychange area is taken over, so that the size of the high-frequency changearea is stable. Therefore, the frequency at which parameters at theencoding time are initialized can be reduced, so that the load imposedon the encoder can be reduced.

Suppression of Contraction of High-Frequency Change Area

As another example, the high-frequency change area identifier 14 dexecutes the following processing when an area identified as ahigh-frequency change area is more contractive than an area which waspreviously identified as the high-frequency change area. That is, thehigh-frequency change area identifier 14 d takes over the areapreviously-identified as the high-frequency change area as a presentidentification result when the degree of the contraction concerned isnot more than a predetermined threshold value.

FIGS. 11A and 11B are diagrams depicting the gist of suppressionconcerning the contraction of the high-frequency change area. FIG. 11Adepicts a change frequency area determining map 90A and anidentification result 91A of a high-frequency change area at a timepoint T1. FIG. 11B depicts a change frequency area determining map 90Band an identification result 91A of a high-frequency change area at atime point T2. The time point T1 and the time point T2 are assumed tosatisfy T1<T2.

As depicted in FIG. 11A, in a case where a mesh joint body having thenumber of change times exceeding a threshold value is obtained on themap 90A and an identification result 91A of a high-frequency change areais obtained, the high-frequency change area is not immediatelycontracted even when the mesh joint body having the number of changetimes exceeding the threshold value is contracted. That is, as depictedin FIG. 11B, even when the mesh joint body having the number of changetimes exceeding the threshold value is contracted at a hatched portionthereof, the identification result 91A of the high-frequency change areais taken over under the condition that the contraction area of thehatched portion is equal to or less than a predetermined thresholdvalue, for example, a half.

Accordingly, even when the motion is partly intermittent in an areawhere moving pictures are actually reproduced, the high-frequency changearea is not intermittently identified, so that frame drop of images canbe prevented from intermittently occurring in the high-frequency changearea. Furthermore, since the identification result of the high-frequencychange area is taken over, the size of the high-frequency change area isstable. Therefore, the initialization frequency of the parameters in theencoding operation can be reduced, so that the load imposed on theencoder can be reduced.

Multistage of Transmission Interval Change

In the first embodiment described above, the moving picture transmissioninterval F2 is set to be shifted between 33 msec as the initial valueand 100 msec. However, the moving picture transmission interval F2 maybe set to be shifted among three or more values. When the moving picturetransmission interval F2 is set to be shifted among three or morevalues, the transmission interval may be set to be longer as the timedifference between the transmission time and the reception time islarger.

Dispersion and Integration

The constituent elements of each device illustrated in the drawings neednot be physically configured as illustrated. That is, the specific modeof dispersion/integration of the respective devices is not limited toone depicted in the figures, and all or some of the devices may beconfigured to be functionally or physically dispersed or integrated inarbitrarily units.

For example, the image transmission processing executed by the firsttransmitter 14 f and the second transmitter 14 h of the server device 10may be integrally performed by one transmitter. Furthermore, the imagereception processing executed by the first receiver 23 b and the secondreceiver 23 e of the client terminal 20 may be integrally performed byone image receiver. Still furthermore, the display control processingexecuted by the first display controller 23 d and the second displaycontroller 23 g of the client terminal may be integrally performed byone display controller.

Image Transmission Program

Various kinds of processing described with respect to the embodimentsdescribed above may be implemented by executing a prepared program witha computer such as a personal computer or a workstation. Therefore, inthe following description, by using FIG. 12, an example of a computerwhich has the same function as the above embodiments and executes animage transmission program will be described.

FIG. 12 is a diagram depicting an example of the computer for executingthe image transmission program according to the first and secondembodiments. As depicted in FIG. 12, a computer 100 has an operatingunit 110 a, a speaker 110 b, a camera 110 c, a display 120 and acommunication unit 130. Furthermore, the computer 100 has a CPU 150, aROM 160, an HDD 170 and a RAM 180. These parts 110 to 180 are connectedto one another through a bus 140.

As depicted in FIG. 12, an image transmission program 170 a performingthe same function as the remote screen controller 14 at the server sidedepicted with respect to the first embodiment is pre-stored in the HDD170. The image transmission program 170 a may be arbitrarily integratedor separated as in the case of the respective constituent elementscontained in each remote screen controller 14 depicted in FIG. 1.Namely, all data stored in the HDD 170 does not always have to be storedin the HDD 170, and a part of data for processes may be stored in theHDD 170.

The CPU 150 reads out the image transmission program 170 a from the HDD170, and develops the read-out image transmission program 170 a into theRAM 180. Accordingly, the image transmission program 170 a functions asan image transmission process 180 a as depicted in FIG. 12. The imagetransmission process 180 a arbitrarily develops various kinds of dataread out from the HDD 170 into corresponding areas allocated to therespective data on the RAM 180, and executes various kinds of processingbased on the thus-developed various kinds of data. The imagetransmission process 180 a contains the processing executed in theremote screen controller 14 depicted in FIG. 1, for example, theprocessing depicted in FIGS. 7 to 9. Furthermore, all the processingunits virtually realized on the CPU 150 do not always have to operate onthe CPU 150, and only the processing unit for the process just has to bevirtually realized.

Incidentally, the image transmission program 170 a does not always haveto be stored in the HDD 170 or the ROM 160 from the beginning. Forexample, each program may be stored in a “portable physical medium” suchas a flexible disk, so-called FD, a CD-ROM, a DVD disk, a magnetoopticaldisk or an IC card that is to be inserted in the computer 100. Thecomputer 100 may obtain and execute each program from the portablephysical medium. Furthermore, each program may be stored in anothercomputer, a server device or the like which is connected to the computer100 through a public line, the Internet, LAN, WAN or the like, and thecomputer 100 may obtain each program from the other computer or theserver device and execute the program.

According to one aspect of the information processing device disclosedin this application, there is attained an effect that drawing delay on ascreen at a client side can be suppressed with suppressing reduction ofoperation response of a thin client.

All examples and conditional language recited herein are intended forpedagogical purposes of aiding the reader in understanding the inventionand the concepts contributed by the inventor to further the art, and arenot to be construed as limitations to such specifically recited examplesand conditions, nor does the organization of such examples in thespecification relate to a showing of the superiority and inferiority ofthe invention. Although the embodiments of the present invention havebeen described in detail, it should be understood that the variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the invention

What is claimed is:
 1. An information processing device includes amemory; and a processor coupled to the memory, wherein the processorexecutes a process comprising: updating an image that includes a desktopscreen image displayed on a terminal device connected through a network,the image representing a processing result based on software and beingstored into an image memory that stores an image; identifying in theimage a high-frequency change area that is an area updated with afrequency not less than a predetermined threshold value during aredetermined period; encoding the high-frequency change area in a movingpicture compression format; transmitting to the terminal device at leastone of an encoded image of a change area in the image, the change areabeing updated with a frequency less than the predetermined thresholdvalue during the predetermined period and the encoded high-frequencychange area, with adding time information thereto, the encodedhigh-frequency change area being transmitted at a first transmissioninterval; receiving the time information from the terminal device;determining based on a difference between the received time informationand a reception time of the time information whether drawing delay ofthe desktop screen image occurs in the terminal device; and startingencoding the change area in a moving picture compression format when thedrawing delay occurs or changing the first transmission interval to asecond transmission interval longer than the first transmission intervalwhen the drawing delay occurs and the encoded high-frequency change areais transmitted at the first transmission interval.
 2. The informationprocessing device according to claim 1, wherein when a plurality ofchange areas exist in the image, the transmitting includes adding thetime information to at least the encoded image of one change area of theplurality of chance areas.
 3. The information processing deviceaccording to claim 1, wherein when the determining includes determiningthat no drawing delay occurs, the transmitting includes transmitting theencoded high-frequency change area at the first transmission interval.4. An image transmission method causing a computer to execute a processcomprising: updating, using a processor, an image that includes adesktop screen image displayed on a terminal device connected through anetwork, the image representing a processing result based on softwareand being stored into an image memory that stores an image; identifying,using the processor, in the image a high-frequency change area that isan area updated with a frequency not less than a predetermined thresholdvalue during a predetermined period; encoding, using the processor, thehigh-frequency change area in a moving picture compression format;transmitting, using the processor, to the terminal device at least oneof an encoded image of a change area in the image, the chance area beingupdated with a frequency less than the predetermined threshold valueduring the predetermined period and the encoded high-frequency changearea, with adding time information thereto, the encoded high-frequencychange area being transmitted at a first transmission interval;receiving, using the processor, the time information from the terminaldevice; determining, using the processor, based on a difference betweenthe received time information and a reception time of the timeinformation whether drawing delay of the desktop screen image occurs inthe terminal device; and starting, using the processor, encoding thechange area in a moving picture compression format when the drawingdelay occurs or changing the first transmission interval to a secondtransmission interval longer than the first transmission interval whenthe drawing delay occurs and the encoded high-frequency change area istransmitted at the first transmission interval.
 5. A non-transitorycomputer readable storage medium having stored therein a program thatcauses a computer to execute an image transmission process comprising:updating an image that includes a desktop screen image displayed on aterminal device connected through a network, the image representing aprocessing result based on software and being stored into an imagememory that stores an image; identifying in the image a high-frequencychange area that is an area updated with a frequency not less than apredetermined threshold value during a predetermined period; encodingthe high-frequency change area in a moving picture compression format;transmitting to the terminal device at least one of an encoded image ofa change area in the image, the change area being updated with afrequency less than the predetermined threshold value during thepredetermined period and the encoded high-frequency change area, withadding time information thereto, the encoded high-frequency change areabeing transmitted at a first transmission interval; receiving the timeinformation from the terminal device; determining based on a differencebetween the received time information and a reception time of the timeinformation whether drawing delay of the desktop screen image occurs inthe terminal device; and starting encoding the change area in a movingpicture compression format when the drawing delay occurs or changing thefirst transmission interval to a second transmission interval longerthan the first transmission interval when the drawing delay occurs andthe encoded high-frequency change area is transmitted at the firsttransmission interval.